This invention relates to a temperature-actuated mixing valve of the general type used to control in-line water temperature in potable hot water systems. Such valves are typically used at the hot water source, such as at a gas or electric hot water heater or boiler. The temperature of the water allowed to flow downstream from the mixing valve is maintained within a predetermined range of temperature by mixing hot and cold water entering the valve on the upstream end. The invention is therefore described with reference to such a hot water system. However, principles of the invention also have application with other liquids and with gases, and for this reason the application is intended to encompass both liquids and gases, and liquids other than water.
Most prior art mixing valves utilize a thermal actuator, which acts as the xe2x80x9cmotorxe2x80x9d of the valve. Such actuators convert thermal energy into mechanical movement. The operating principle of most such devices is based upon the large increase in volume of a thermosensitive material such as wax which, when heated, changes from a solid to a liquid. When such a thermosensitive material is enclosed within a confined space, heating causes the material to expand against a piston to perform work. In some cases such actuators are either provided with two oppositely-acting pistons to increase the range of motion, or two such actuators are placed end-to-end to accomplish the same function. By incorporating a thermal actuator into a mixing valve, hot and cold supply pressures and temperatures can be regulated.
A common problem in the use of such devices is that if the shuttle has moved as far as it can move within the valve, but the piston of the thermal actuator is still trying to move, there must be some means of consuming this extra travel. Otherwise the valve can be damaged or destroyed. This is most often accomplished in the prior art by the use of an overtravel spring mounted around an adjusting bolt in the top of the valve. This solution creates several additional problems. First, this arrangement adds height to the mixing valve, which may prevent or restrict use in confined areas, or promote breakage under impact. Second, the overtravel spring must be preloaded, requiring a means for retaining the spring on the adjusting bolt. Finally, in applications where two thermal actuators are used back-to-back, there must be some way to retain both elements in the shuttle.
In addition, mixing valves are often difficult to disassemble for repair or maintenance, and require the use of tools, often in confined spaces.
The design features of the present invention solve the known prior art problems simply and efficiently.
Therefore, it is an object of the invention to provide a mixing valve which is compact.
It is another object of the invention to provide a mixing valve which is easy to disassemble.
It is another object of the invention to provide a mixing valve in which the overtravel spring is integral with the shuttle assembly.
It is another object of the invention to provide a mixing valve in which the shuttle ccages the thermal element or elements, which permitting unrestricted movement within the full range of movement.
It is another object of the invention to provide a mixing valve wherein the overtravel spring is remote from and operates independently of the adjustment bolt.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a temperature-actuated mixing valve for controlling outlet temperature in a fluid flow system including a valve housing having first and second fluid supply inlets for introducing first and second respective supply fluids and a fluid outlet for dispensing a fluid at a predetermined outflow temperature. The mixing valve includes a shuttle assembly positioned in the housing. The shuttle assembly comprises a valve member mounted for movement within the housing responsive to the temperature of the supply fluids to vary the mixture ratio of the first and second supply fluids as required to dispense fluid at the predetermined outflow temperature. A shuttle member is positioned within the valve member and is moveable as a unit therewith within a predetermined range of motion responsive to supply fluid temperature variation. The shuttle member includes an elongate grip pad for permitting the shuttle member to be manually removed from the valve housing without the need for tools. A thermal actuator is provided of the type which converts thermal energy into mechanical movement by movement of a piston. A first end of the thermal element engages the movable shuttle member and an opposing second end engages a stationary portion of the housing whereby movement of the piston of the thermal actuator produces corresponding movement of the valve member. An overtravel spring is captured in a compressed condition between the valve member and the shuttle member for maintaining the shuttle member and the valve member in a stationary condition relative to each other within the predetermined range of motion of the valve member and for permitting movement of the shuttle member relative to the valve member sufficient to accommodate movement of the piston of the thermal actuator when the valve member has reached its limit of travel without accommodating the full extent of movement of the piston of the thermal actuator.
According to one preferred embodiment of the invention, the valve member is generally cylindrical and includes sealing means for sealing the valve member against fluid flow between the valve member and adjacent cylindrical walls of the valve housing.
According to another preferred embodiment of the invention, the shuttle member includes retaining means for retaining the thermal actuator within the shuttle member while permitting movement of the piston responsive to the temperature of the inlet fluids.
According to yet another preferred embodiment of the invention, the retaining means comprises a plurality of elongate fingers axially aligned with the longitudinal axis of the thermal actuator, each of the fingers having a radially inwardly-extending detent for interfering with movement of the thermal actuator beyond a predetermined range of motion for movably-capturing the thermal actuator within the shuttle member.
According to yet another preferred embodiment of the invention, the grip pad extends along the longitudinal axis of the shuttle member.
According to yet another preferred embodiment of the invention, the valve member includes an annular shoulder defining a support for the overtravel spring. The valve member includes locking means for receiving and locking the shuttle member within the valve member. The locking means cooperates with the overtravel spring for maintaining the shuttle member and the valve member in the stationary condition relative to each other.
According to yet another preferred embodiment of the invention, the locking means comprises a plurality of locking channels formed within the area of the valve member accommodated by the overtravel spring, each of the locking channels having a first segment communicating with an inwardly-facing end of the valve member, a second segment communicating with the first segment and extending peripherally around inner wall of the valve member and a third segment spaced apart from the first segment, communicating with the second segment and terminating at a blind end within the inner walls of the valve member, the plurality of locking channels adapted to receive respective ones of a plurality of locking tabs carried by the shuttle member and lock the shuttle member in the valve member by compressing the overtravel spring and passing the plurality of locking tabs through the first and second segments and to the blind end of the third segment of the locking channels.
According to yet another preferred embodiment of the invention, the shuttle member comprises an elongate stem having an annular bore for receiving the thermal actuator therein for movement therein, retaining means for retaining the thermal actuator in the bore and locking means for locking the stem in the valve member.
According to yet another preferred embodiment of the invention, the valve housing includes an adjusting bolt engaging an end of the thermal actuator remote from the valve member for permitting longitudinal adjustment of the thermal actuator relative to the valve member.
According to yet another preferred embodiment of the invention, the thermal actuator comprises a pair of thermal actuators for increasing the effective range of temperature-responsive motion.
According to yet another preferred embodiment of the invention, the retaining means comprises a cage within which the thermal actuator is captured.
An embodiment of the method according to the invention controls outlet temperature in a fluid flow system including a valve housing having first and second fluid supply inlets for introducing first and second respective supply fluids and a fluid outlet for dispensing a fluid at a predetermined outflow temperature, the mixing valve including a shuttle assembly positioned in the housing. The method comprises the steps of mounting a valve member for movement within the housing responsive to the temperature of the supply fluids to vary the mixture ratio of the first and second supply fluids as required to dispense fluid at the predetermined outflow temperature. A shuttle member is positioned within the valve member as a unit with the valve member within a predetermined range of motion responsive to supply fluid temperature variation. The shuttle member includes an elongate grip pad for permitting the shuttle member to be manually removed from the valove housing without the need for tools. A thermal actuator is provided of the type which converts thermal energy into mechanical energy by movement of a piston wherein a first end of the thermal element engages the movable shuttle member and an opposing second end engages a stationary portion of the housing whereby movement of the piston of the thermal actuator produces corresponding movement of the valve member. The shuttle member and the valve member are maintained in a stationary condition relative to each other within the predetermined range of motion of the valve member while permitting movement of the shuttle member relative to the valve member sufficient to accommodate movement of the piston of the thermal actuator when the valve member has reached its limit of travel without accommodating the full extent of movement of the piston of the thermal actuator.
Another embodiment of the method according to the invention comprises the step of retaining the thermal actuator within a cage forming a part of the shuttle member for permitting movement of the thermal actuator within its range of motion while preventing the thermal actuator from falling out of the shuttle assembly.
According to another preferred embodiment of the invention, a method is disclosed for controlling outlet temperature in a mixing valve of a fluid flow system includes a valve housing having first and second fluid supply inlets for introducing first and second respective supply fluids and a fluid outlet for dispensing a fluid at a predetermined outflow temperature, the mixing valve including a shuttle assembly positioned in the housing and carrying a thermal actuator responsive to the temperature of fluid entering the mixing valve for controlling the ratio of the respective supply fluids to regulate the outflow temperature of the fluid. The method comprises the step of forming the shuttle assembly from a shuttle member and a valve member releasably-attached together. The shuttle member includes an elongate grip pad for permitting the shuttle member to be manually removed from the valve housing without the need for tools. The method further includes the steps of retaining an overtravel spring between the shuttle member and the valve member, moving the shuttle member and the valve member as a unit responsive to the thermal actuator when regulating the flow of fluid flowing into the mixing valve, and moving the shuttle member relative to the valve member when compensating for overtravel of the thermal actuator.